1. Field of the Invention
The present invention relates to a method and apparatus for the deconvolution of spectra, or of fragmentation or cracking patterns. More particularly, the present invention is related to a deconvolution technique operating in conjunction with a mass spectrometer.
2. Description of Related Art
Regardless of the mass spectrometer used, generally whenever a mass spectrum of compound is collected it is often up to an experienced process chemist to analyze and interpret the mass spectrum by hand. A mass spectrum can also be used to determine a fragmentation pattern or cracking pattern. The process chemist attempts to match the mass spectrum of the unknown compound against known compound spectra. A process chemist may require extended amounts of time to deconvolute (i.e., interpret) a mass spectrum and determine the elements or molecules that are in the unknown sample. Furthermore, the process chemist must remove or manually xe2x80x9cfilter outxe2x80x9d all known or determined information from the mass spectrum as the deconvolution process continues.
During manufacturing of highly pure substances, such as silicon wafers or semiconductor devices, it is important to determine the composition of the wafer environment in order to detect problems with the process. This must be done quickly to maximize the value in a manufacturing process.
Thus, what is needed is a system analytical instrument that incorporates a methodology adapted to deconvolute a mass spectrum or fragmentation pattern using an intuitive approach that is similar to that of an experienced process chemist. Such a system may be able to test substances in a manufacturing process in a timely manner such that the manufacturing process is not significantly slowed and alarms can be exhibited when predetermined substances (contaminants) are found within the manufacturing process. The system may be associated with a mass spectrometer.
An exemplary embodiment of the present invention provides a mass spectrometer with a computer aided methodology for analyzing a sample and its associated fragmentation or cracking patterns. A deconvolution compound data library is selected by a user to be utilized by the computer system. The deconvolution library comprises compounds in a specific or predetermined order. Each compound entry includes an ionization energy for the compound and associated peaks or m/z values with associated abundance values. The compound library may have a few to as many as about 150 compound entries contained therein. The specific order of the compound library is very important because it mimics the deconvolution process that an experienced process chemist would utilize to deconvolute a fragmentation pattern from a sample taken from a known or somewhat known process or substance. The computer system deconvolutes the fragmentation pattern using the ordered compound library such that if a xe2x80x9cfingerprintxe2x80x9d of a compound from the compound library is found in the fragmentation pattern, then at least one full peak (m/z value and its associated abundance value) is removed from the fragmentation pattern prior to searching for the existence of the next compound from the compound library in the fragmentation pattern. Found compound remainder values can also be removed from the fragmentation pattern.
The exemplary embodiment can provide indications, such as visual or audible alarms, if a compound that is considered a contaminant is found in the fragmentation pattern. The exemplary embodiment is especially useful in manufacturing processes wherein purity is important. Examples of such processes include physical vapor (PVD) deposition and chemical vapor deposition (CVD), utilized, for example, in semiconductor manufacturing. An exemplary embodiment of the present invention can be incorporated into such a manufacturing process and can monitor purity and quality criteria associated with the process or manufactured items.